1. Field of the Invention
This invention relates in general to biological, biochemical and chemical assays, and more particularly, to a sampling and filtration device comprising a stack of multiwell plates which is useful in processing such assays.
2. Description of the Related Art
Multiwell test plates used for isotopic and non-isotopic in-vitro assays are well known in the art and are exemplified, for example, by those described in U.S. Pat. Nos. 3,111,489; 3,540,856; 3,540,857; 3,540,858; 4,304,865; 4,948,442; and 5,047,215. Typically, such test plates have been standardized in the form of the so-called micro-titre plate that provides, in one example, 96 depressions or cylindrical wells of about 0.66 cm in diameter and 1.3 cm deep, arranged in a 12×8 regular rectangular array spaced about 0.9 cm center-to-center.
Selected wells in such a test-plate are used to incubate respective microcultures, followed by further processing to harvest the incubated material. Each well typically includes a filtration element so that, upon application of a vacuum to one side of the plate, fluid in each well is expressed through the filter leaving solids, such as bacteria, debris and the like, entrapped in the well. In typical use, specimens from up to 96 different individuals may be respectively inserted in corresponding wells in the multiwell plate in the course of an assay, the specimens typically all being inserted prior to filtration and completion of the assay.
Oftentimes, it is necessary to transfer biological/chemical samples from one multiwell test-plate to another multiwell test plate. The conventional approach to transferring samples is to pipette the samples from the first test plate to the second test plate. However, this approach can be time consuming and difficult depending upon the plate configurations between which samples are being transferred. For example, micro-titre plates providing 384 or 864 cylindrical wells arranged in a regular rectangular array have recently become available. Since each well of a 96-well plate can hold 400 μl or more of sample, while a well of a 384-well plate can only hold, for example, 100 μl of sample, it is conventionally necessary to pipette sample from each well of the 96-well plate to four different wells of the 384-well plate. Obviously, this procedure can be tedious.
With the availability of the new multiwell plates, various assay processing enhancements are desirable. In particular, enhancements in the transfer process are needed for moving samples from, for example, a 96-well plate to a 384- or 864-well plate. The present invention is directed to providing these processing enhancements for the transfer of samples between different multiwell plates.